Metal-Induced Coordination Inversion and Carbon-Nitrogen Bond Rearrangement. Structurally Characterized Phenyl Isocyanate Inserted into Aluminum Methyl Compounds and O- and N-Bound Aluminum Compounds

Article abstract of DOI:10.1021/ic035261z

[C₄H₃N(CH₂NMe₂)-2]AlMe ₂ (1) is prepared in 88% yield by the reaction of substituted pyrrole [C₄H₄N(CH₂NMe₂)-2] with 1 equiv of AlMe₃ in methylen

Full text of DOI:10.1021/ic035261z

Inorg. Chem. 2004, 43, 2183−2188
Metal-Induced Coordination Inversion and Carbon−Nitrogen Bond
Rearrangement. Structurally Characterized Phenyl Isocyanate Inserted
into Aluminum Methyl Compounds and O- and N-Bound Aluminum
Compounds
Chia-Fu Tsai, Hsing-Jen Chen, Jr-Chiuan Chang, Cheng-Hsiang Hung, Chun-Chia Lai,
Ching-Han Hu, and Jui-Hsien Huang*
Department of Chemistry, National Changhua UniVersity of Education, Changhua, Taiwan 50058
Received October 30, 2003
[C H N(CH NMe2)-2]AlMe2 (1) is prepared in 88% yield by the reaction of substituted pyrrole [C H N(CH NMe2)-2]
4
3
2
4
4
2
with 1 equiv of AlMe3 in methylene chloride. Reaction of compound 1 with 1 equiv of phenyl isocyanate in toluene
generates a seven-membered cycloaluminum compound {C H N[CH NPh(CONMe2)]-2}AlMe2 (2). The phenyl
4
3
2
isocyanate was inserted into the aluminum and dimethylamino nitrogen bond and induced an unusual rearrangement
which results in C−N bond breaking and formation. A control experiment shows that the reaction of substituted
pyrrole [C H N(CH NMe2)-2] with 1 equiv of phenyl isocyanate in diethyl ether yields a pyrrolyl attached urea
4
4
2
derivative {C H N(CH NMe2)-2-[C(dO)NHPh]-1} (3). The demethanation reaction of AlMe3 with 1 equiv of 3 in
4
3
2
methylene chloride at 0 °C afforded O-bounded and N-bounded aluminum dimethyl compounds {C H N(CH -
4
3
2
NMe2)-2-[C(dO)NPh]-1}AlMe2 (4a) and {C H N(CH NMe2)-2-[CO(dNPh)]-1}AlMe2 (4b) in a total 78% yield after
4
3
2
recrystallization. Both 4a and 4b are observed in 1H NMR spectra; however, the relative ratio of 4a and 4b depends
on the solvent used. Two equivalents of AlMe3 was reacted with 3 in methylene chloride to yield a dinuclear
aluminum compound AlMe3{C H N(CH NMe2)-2-[C(dO)NPh]-1}AlMe2 (5). Reaction of 5 with another equivalent
4
3
2
of ligand 3 results in the re-formation of compounds 4a and 4b.
Introduction
synthesis and characterization of organic isocyanate com-
pounds is of great interest because of their possible relevance
in intermediates of catalytic reactions. Moreover, the orga-
nometallic isocyanate compounds can also serve as useful
models for the chemical behavior of carbon dioxide.4 The
reactions of organic isocyanates with organometallic com-
pounds generally involve insertion reactions,5 coupling
reactions,6 and catalytic reactions.7 We have been interested
in the reactions of substituted pyrrolyl ligands8 with group
Regarding the organometallic compounds, aluminum
compounds have been widely used in industry and research
due to their availability and decreased expensiveness.1 Large
numbers of organoaluminum compounds have been synthe-
sized from aluminum halide or aluminum alkyl precursors
and converted to other aluminum compounds. Organic
isocyanates represent an important class of reactive sub-
stances in organic synthesis2 and polymer chemistry.3 The
* Author to whom correspondence should be addressed. E-mail: juihuang@
cc.ncue.edu.tw.
(4) (a) Braunstein, P.; Matt, D.; Nobel, D. Chem. ReV. 1988, 88, 747. (b)
Behr, A. Angew. Chem., Int. Ed. Engl. 1988, 27, 661. (c) Floriani, C.
Pure Appl. Chem. 1982, 54, 661.
(5) (a) Lappert, M. F.; Prokai, B. AdV. Org. Chem. 1967, 5, 225.(b) Zhou,
X.; Zhang, L.; Cai, R.; Weng, L.; Huang, Z.; Wu, Q. Organometallics
2001, 20, 5700.
(1) (a) Murahashi, S.-I.; Takaya, H. Acc. Chem. Res. 2000, 33, 225. (b)
Tilley, T. D. Acc. Chem. Res. 1993, 26, 22. (c) Gardiner, M. G.;
Raston, C. L. Coord. Chem. ReV. 1997, 166, 1. (d) Cucinella, S.;
Mazzei, A.; Marconi, W. Inorg. Chim. Acta ReV. 1970, 4, 51. (e)
Downs, A. J.; Pulham, C. R. AdV. Inorg. Chem. 1994, 41, 171. (f)
Cowley, A. H.; Gabba¨ı, F. P.; Isom, H. S.; Decken, A. J. Organomet.
Chem. 1995, 500, 81. (g) Wehmschulte, R. J.; Power, P. P. Polyhedron
2000, 19, 1649.
(6) Braunsteim, P.; Nobel, D. Chem. ReV. 1989, 89, 1927 and references
therein.
(7) (a) Ulrich, H.; Tucker, B.; Sayigh, A. A. R. Tetrahedron Lett. 1967,
1731. (b) Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1984, 23,
539.
(2) La´bbe´, G. Synthesis 1987, 525.
(3) Sanuder, J. H.; Frisch, K. C. Polyurethane; Wiley-Interscience: New
York, 1962.
(8) (a) Herz, W.; Dittmer, K. J. Am. Chem. Soc. 1947, 69, 1698. (b) Kim,
H.; Elsenbaumer, R. L. Tetrahedron Lett. 1998, 39, 1087.
10.1021/ic035261z CCC: $27.50 © 2004 American Chemical Society
Published on Web 02/27/2004
Inorganic Chemistry, Vol. 43, No. 6, 2004 2183

Tsai et al.
Scheme 1
Table 1. Crystallographic Data for Compounds 1, 2, 3, and 4b, and 5
1
2
3
4b
5
empirical formula
formula weight
temp (K)
C9H17AlN2
180.23
150(1)
C16H22AlN3O
299.35
293(2)
C14H17N3O
243.31
293(2)
C16H22AlN3O
299.35
293(2)
C19H31Al2N3O
371.43
293(2)
crystal system
space group
a, Å
b, Å
c, Å
monoclinic
P21/c
8.6007(2)
8.9211(2)
14.3956(2)
90
93.0406(9)
90
1102.99(4)
4
monoclinic
P21/c
8.3661(12)
21.722(3)
9.7502(14)
90
102.323(3)
90
1731.1(4)
4
monoclinic
P21/c
10.8566(19)
10.3255(18)
12.663(2)
90
105.494(3)
90
1367.9(4)
4
monoclinic
P21/c
13.274(2)
10.5400(17)
12.2178(19)
90
101.194(4)
90
1676.9(5)
4
monoclinic
P21/n
9.3229(10)
13.5500(15)
17.8097(19)
90
91.595(2)
90
2248.9(4)
4
R, deg
â, deg
γ, deg
volume, Å3
Z
density (calcd), mg/m3
abs coeff, mm-1
F(000)
1.085
0.139
392
1.149
0.120
640
1.181
0.077
520
1.233
0.126
664
1.097
0.140
800
crystal size
θ range, deg
reflns collected
independent reflns
0.50 × 0.35 × 0.35
2.37-27.50
16428
0.45 × 0.35 × 0.24
1.87-20.82
6135
0.30 × 0.25 × 0.20
1.95-27.52
8458
0.28 × 0.25 × 0.20
1.56-27.56
10379
0.45 × 0.30 × 0.24
1.89-27.53
14034
2523
1817
3140
3815
5139
(Rint ) 0.0483)
2523/0/110
1.084
R1 ) 0.0399
wR2 ) 0.1130
R1 ) 0.0513
wR2 ) 0.1225
0.266 and -0.249
(Rint ) 0.0816)
1817/0/195
0.982
R1 ) 0.0726
wR2 ) 0.2072
0.1120
(Rint ) 0.0312)
3140/0/165
0.853
R1 ) 0.0512
wR2 ) 0.1460
0.0922
(Rint ) 0.1251)
3815/0/194
0.802
R1 ) 0.0811
wR2 ) 0.1891
0.1716
(Rint ) 0.0576)
5139/0/233
0.725
R1 ) 0.0421
wR2 ) 0.0842
R1 ) 0.1081
wR2 ) 0.0948
0.192 and -0.217
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
wR2 ) 0.2200
0.274 and -0.277
wR2 ) 0.1665
0.446 and -0.176
wR2 ) 0.2292
0.323 and -0.664
largest diff peak and hole, e Å3
139 and early transition metals10 and their reactivites toward
small organic molecules. Herein we report the reactions of
phenyl isocyanate with substituted pyrrolyl aluminum com-
pounds, and an unusual rearrangement which results in
nitrogen-carbon bond breaking and formation. Moreover,
Lewis acid induced O- and N-bound inversion reactions of
aluminum compounds are also reported.
crystallized product. The 1H and 13C NMR spectra of
compound 1 in CDCl3 are all as expected; the H NMR
1
spectra of methylene and dimethylamino groups of the
substituted pyrrolyl exhibit singlet resonance at δ 3.88 and
2.56, respectively, and the dimethyl group of the AlMe2
fragment appears at -0.68. The single-crystal structure of
compound 1 was determined, and the molecular structure is
depicted in Figure 1. The summaries of data collection
parameters are shown in Table 1, and selected bond distances
and angles are listed in Table 2. The four-coordinate
compound 1 represents as a tetrahedral structure with the
bite angle of the substituted pyrrolyl ligand N(1)-Al-N(2)
of 85.40(5)°.
Results and Discussion
The dimethyl aluminum compound [C4H3N(CH2NMe2)-
2]AlMe2 (1) is readily prepared in 90% yield by the reaction
of substituted pyrrole [C4H4N(CH2NMe2)-2] with 1 equiv
of AlMe3 in methylene chloride (Scheme 1).
Reaction of compound 1 with 1 equiv of phenyl isocyanate
in toluene generates an unusual seven-membered cycloalu-
minum compound {C4H3N[CH2NPh(CONMe2)]-2}AlMe2
(2) as shown in Scheme 1. The 1H NMR spectra of
methylene and dimethylamino groups of the substituted
pyrrolyl of 2 exhibit singlet resonances at δ 4.76 and 2.72,
respectively, and the dimethyl group of the AlMe2 fragment
appears as a singlet at δ -0.64. The 13C NMR gated
decoupling spectrum exhibited a singlet resonance at 161.5
which can be assigned to the NCO carbonyl. The proposed
mechanism for the reaction of 1 with PhNCO is shown in
Compound 1 was obtained in an oily form following
workup. However, it solidified after immersion of the flask
in liquid nitrogen, and the solid compound 1 remained as a
solid after warming to room temperature. Solid compound
1 can be recrystallized from methylene chloride to yield
(9) (a) Huang, J.-H.; Kuo, P.-C.; Lee, G.-H.; Peng, S.-M. J. Chin. Chem.
Soc. 2000, 27, 1191. (b) Huang, J.-H.; Chi, L.-S.; Huang, F.-M.; Kuo,
P.-C.; Lee, G.-H.; Peng, S.-M. J. Chin. Chem. Soc. 2000, 27, 895. (c)
Huang, J.-H.; Chi, L.-S.; Yu, R.-C.; Jiang, G. J.; Yang, W.-T.; Lee,
G.-H.; Peng, S.-M. Organometallics 2001, 20, 5788.
(10) Huang, J.-H.; Chen, H.-J.; Chang, J.-C.; Lee, G.-H.; Peng, S.-M.
Organometallics 2001, 20, 2647.
2184 Inorganic Chemistry, Vol. 43, No. 6, 2004

Reactions of PhNCO and Pyrrolyl Aluminum Compounds
Scheme 2
Table 2. Bond Lengths (Å) and Angles (deg) for Compounds 1, 2, 3,
4b, and 5
1
Al-N(1)
Al-C(1)
1.8785(13) Al-N(2)
1.9632(17) Al-C(2)
2.0242(13)
1.9556(18)
N(1)-Al-C(2)
C(1)-Al-C(2)
N(2)-Al-C(2)
117.31(7)
119.46(8)
109.88(7)
N(1)-Al-C(1)
N(1)-Al-N(2)
C(1)-Al-N(2)
112.12(7)
85.40(5)
106.67(7)
2
Al(1)-O(1)
Al(1)-C(15)
O(1)-C(12)
N(3)-C(12)
1.828(5)
1.932(7)
1.276(8)
1.339(8)
Al(1)-N(1)
Al(1)-C(16)
N(2)-C(12)
1.898(6)
1.956(7)
1.362(9)
O(1)-Al(1)-N(1)
N(1)-Al(1)-C(15)
N(1)-Al(1)-C(16)
101.4(3)
112.8(3)
109.2(3)
O(1)-Al(1)-C(15)
O(1)-Al(1)-C(16)
105.4(3)
106.6(3)
C(15)-Al(1)-C(16) 119.5(3)
3
N(1)-C(8)
N(2)-C(8)
1.415(2)
1.343(2)
C(8)-O(1)
N(2)-C(9)
1.213(2)
1.415(2)
O(1)-C(8)-N(1)
N(2)-C(8)-N(1)
119.42(17) O(1)-C(8)-N(2)
114.58(15) C(8)-N(2)-C(9)
125.96(18)
124.57(14)
Figure 1. Molecular structure of compound 1. The thermal ellipsoids were
drawn at 50% probability, and all hydrogen atoms were omitted for clarity.
4b
Al(1)-O(1)
C(10)-O(1)
C(10)-N(3)
1.785(3)
1.317(5)
1.270(5)
Al(1)-N(2)
C(10)-N(1)
2.015(4)
1.429(5)
O(1)-Al(1)-N(2)
97.30(16)
C(10)-N(3)-C(11) 119.0(4)
N(3)-C(10)-N(1)
116.2(4)
5
Al(1)-N(3)
Al(1)-C(1)
Al(2)-O(1)
Al(2)-C(4)
C(13)-N(3)
1.932(2)
1.939(2)
1.894(2)
1.970(2)
1.314(2)
Al(1)-N(2)
Al(1)-C(2)
Al(2)-C(3)
Al(2)-C(5)
C(13)-O(1)
2.007(2)
1.945(2)
1.968(2)
1.964(2)
1.265(2)
N(3)-Al(1)-N(2)
O(1)-C(13)-N(1)
98.16(7)
N(3)-C(13)-N(1)
116.60(18)
132.94(13)
125.85(19) C(13)-O(1)-Al(2)
in the range between single and double bonds in comparison
to the bond lengths of CdO (1.293(3) Å) and C-N (1.378-
(3) and 1.360(4) Å) of DMPU. As suggested in Scheme 2,
the unpaired electrons of the urea group of 2 are resonance
delocalized between the CN and CO bonds, which results
in partially doubly bonded C(12)-N(3) and C(12)-O(1).
In view of the covalent model, the N(3) would be partially
positively charged and O(1) would be partially negatively
charged. Indeed, the electrostatic potential on the electron
isodensity surface derived from density functional theory
using B3LYP/6-31G* confirms that O(1) is negatively
charged, while N(3) is positively charged.12 A figure
representing the electrostatic potential of compound 2 is
shown in Supporting Information.
Figure 2. Molecular structure of compound 2. The thermal ellipsoids were
drawn at 50% probability, and all hydrogen atoms were omitted for clarity.
Scheme 2. The phenyl isocyanate was inserted into the
aluminum and dimethylamino nitrogen bond and induced an
unusual rearrangement which results in C-N bond breaking
and formation.
The molecular geometry of 2 was confirmed by X-ray
crystallography. The colorless crystals of 2 were obtained
by cooling of a saturated solution in methylene chloride. The
molecular structure of 2 is depicted in Figure 2. Selected
bond distances and angles of 2 are shown in Table 2. The
molecular structure of N,N-dimethyl-N-phenylurea (DMPU)11
was taken into account for comparison. The bond lengths
C(12)-O(1) (1.276(8) Å) and C(12)-N(3) (1.339(8) Å) are
The reaction of isocyanate with amine to form urethane
is common.13 Rearrangement involving C-N bond breaking
(12) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.; Yang,
W.; Parr, R. G. Phys. ReV. B 1988, 37, 785.
(13) Fieser, L. F.; Fieser, M. Reagents for Organic Synthesis; Wiley: New
York, 1967; Vol. 1.
(11) The molecular structure of DMPU was solved, and CIF files can be
found in the Supporting Information.
Inorganic Chemistry, Vol. 43, No. 6, 2004 2185

Tsai et al.
Scheme 3
Figure 3. Molecular structure of compound 3. The thermal ellipsoids were
drawn at 50% probability, and all hydrogen atoms were omitted for clarity.
and formation can be found in the literature.14 However, the
metal induced rearrangement reaction in Scheme 1 was
unusual. A control experiment was performed for comparison
with the reactions in Scheme 1 using the nonmetal reaction
of phenyl isocyanate with substituted pyrrolyl ligand. The
reaction of substituted pyrrole [C4H4N(CH2NMe2)-2] with
1 equiv of phenyl isocyanate in diethyl ether yields a pyrrolyl
attached urea derivative {C4H3N(CH2NMe2)-2-[C(dO)-
NHPh]-1} (3) (Scheme 3). No rearrangement as shown in
Scheme 2 was observed. The 1H NMR spectra of 3 showed
a downfield singlet (δ 12.91) which can be assigned to the
NH proton. The 13C NMR spectrum exhibited a high field
singlet at δ 149.1 that is assigned to the carbonyl group of
the urea of 3. However, the unambiguous molecular geometry
was determined by X-ray single-crystal structure determi-
nation. The molecular structure of 3 is shown in Figure 3.
Selected bond distances and angles are listed in Table 2. The
bond distances of C(8)-O(1) (1.213(2) Å) and C(8)-N(2)
(1.343(2) Å) are in the range of double and single bond,
respectively, in comparison to DMPU.
Figure 4. Molecular structure of compound 4b. The thermal ellipsoids
were drawn at 50% probability, and all hydrogen atoms were omitted for
clarity.
[C(dO)NPh]-1}AlMe2 (4a) and {C4H3N(CH2NMe2)-2-[CO-
(dNPh)]-1}AlMe2 (4b) (types A and B in Scheme 4) in a
total 78% yield after recrystallization. Both 4a and 4b are
observed in 1H NMR spectra; however, the relative ratio of
4a and 4b depends on the deuterium solvent used. The
average ratio of 4a/4b is ca. 1.0 in CDCl3 and ca. 0.5 in
C6D6 at room temperature, which indicates that 4a and 4b
are interconverting at room temperature and that the ratio is
affected by the polarity of solvents. Two singlets for the
NMe2 moiety at δ 2.47 and 2.43 and two singlets for the
AlMe2 at δ -0.98 and -1.29 are observed for 4a and 4b in
CDCl3; however, we were not able to distinguish which went
with which compound due to the 1:1 ratio.
The molecular structure of 4b was determined by X-ray
crystallography, and the molecular structure is depicted in
Figure 4. Selected bond distances and angles are listed in
Table 2. The structure of 4b revealed an unsymmetrical
geometry with the aluminum bonded with 3 forming a
puckered seven-member ring. The bond distances of C(10)-
N(3) (1.270(5) Å) and C(10)-O(1) (1.317(5) Å) are clearly
identified as a CdN double bond and a C-O single bond,
Compound 3 represents a new type of polydentate ligand
with multiple coordination sites which may bond to metal(s)
via sigma or coordinating bonds. Scheme 4 represents some
possible metal complex geometries. The reactions of the
polydentate ligand 3 with trimethyl aluminum are sum-
marized in Scheme 3. The demethanation reaction of
trimethyl aluminum with 1 equiv of 3 in methylene chloride
at room temperature afforded O-bounded and N-bounded
aluminum dimethyl compounds {C4H3N(CH2NMe2)-2-
(14) For examples of C-N bond breaking and formation, see: (a)
Bhattacharyya, S.; Weakley, T. J. R.; Chaudhury, M. Inorg. Chem.
1999, 38, 5453. (b) Saha, A.; Ghosh, A. K.; Majumdar, P.; Mitra, K.
N.; Mondal, S.; Rajak, K. K.; Falvello, L. R.; Goswami, S. Organo-
metallics 1999, 18, 3772. (c) Barluenga, J.; Toma´s, M.; Rubio, E.;
Lo´pez-Pelegr´ın, J. A.; Garc´ıa-Granda, S.; Pe´rez-Priede, M. J. Am.
Chem. Soc. 1999, 121, 3065. (d) Khumtaveeporn, K.; Alper, H. Acc.
Chem. Res. 1995, 28, 414. (e) Wolfe, J. P.; Wagaw, S.; Buchwald, S.
L. J. Am. Chem. Soc. 1996, 118, 7215. (f) Izod, K.; O’Shaughnessy,
P.; Clegg, W. Organometallics 2002, 21, 641. (g) Ishikawa, T.;
Kawakami, M.; Fukui, M.; Yamashita, A.; Urano, J.; Saito, S. J. Am.
Chem. Soc. 2001, 123, 7734.
2186 Inorganic Chemistry, Vol. 43, No. 6, 2004

Reactions of PhNCO and Pyrrolyl Aluminum Compounds
Scheme 4
respectively. The bond angle of C(10)-N(3)-C(11) (119.0-
(4)°) represents the N(3) belonging to a sp2 hybridization
mode with a lone pair of electrons left noncoordinated.
The PhNCdO and PhNdC moieties of 4a and 4b provide
good electron-donating sites which might act as good
candidates for coordinating to another Lewis acid metal
center. In this regard, 2 equiv of AlMe3 was reacted with 3
in methylene chloride at 0 °C to yield a dinuclear aluminum
compound AlMe3{C4H3N(CH2NMe2)-2-[C(dO)NPh]-1}-
AlMe2 (5) (Scheme 3). Compound 5 can be classified as
type D geometry of Scheme 4, and no type E was observed
1
spectroscopically. The H NMR spectra of methylene and
dimethylamino groups of the substituted pyrrolyl of 5 exhibit
singlet resonances at δ 3.92 and 2.56, respectively. The
methyl groups of the AlMe3 and AlMe2 fragment appear as
two singlets at δ -1.23 and -1.27 with the relative ratio of
2:3. Further studies show that reaction of 5 with another
equivalent of ligand 3 results in the re-formation of com-
pounds 4a and 4b.
Figure 5. Molecular structure of compound 5. The thermal ellipsoids were
drawn at 50% probability, and all hydrogen atoms were omitted for clarity.
Conclusions
The colorless single crystals of 5 were obtained from a
solution of concentrated methylene chloride, and its structure
was determined by X-ray crystallography. The X-ray struc-
ture is shown in Figure 5, and a selection of bond distances
and angles are collected in Table 2. The structure contains
two aluminum atoms, an AlMe2 moiety and an AlMe3
molecule, both bonded to the multidentate ligand 3. The
AlMe2 moiety is bonded to the nitrogen atoms of dimeth-
ylamino and PhNCO fragments, leading to a tetrahedral
geometry around Al(1). The bond angle of N(3)-Al(1)-
N(2) at 98.16(7)° is smaller than the average sp3 bond angle
(average 109.28°), which was attributed to the ring con-
straints of the seven-membered cycloaluminum fragment.
The Lewis acidic AlMe3 molecule forms an acid-base
compound with the oxygen atom of the PhNCO fragment
which also results in a tetrahedral geometry around Al(2).
The bond lengths of Al-N and Al-C are all in the normal
range as compared to other aluminum compounds in the
literature.15
We have found a novel metal induced carbon-nitrogen
bond rearrangement in the reaction of 1 and PhNCO with
the formation of a seven-membered-ring aluminum com-
pound. A control experiment proved that the C-N bond
rearrangement can only occur in the presence of aluminum.
Compound 3, obtained from the reaction of substituted
pyrrole and PhNCO, represents a new type of polydentate
ligand which can coordinate to metals in a variety of binding
modes. Again, Lewis acidic aluminum metal plays an
important role for the bonding geometry of 3. The potential
ability for the versatile ligand 3 to bring two different metals
simultaneously and their reaction activities toward small
organic molecules are under investigation.
(15) (a) Hogerheide, M. P.; Wesseling, M.; Jastrzebski, J. T. B. H.;
Boersma, J.; Kooijman, H.; Spek, A. L.; van Koten, G. Organome-
tallics 1995, 14, 4483. (b) Schiefer, M.; Hatop, H.; Roesky, H. W.;
Schmidt, H.-G.; Noltemeyer, M. Organometallics 2002, 21, 1300. (c)
Jegier, J. A.; Atwood, D. A. Inorg. Chem. 1997, 36, 2034. (d) Fryzuk,
M. D.; Giesbrecht, G. R.; Olovsson, G.; Rettig, S. J. Organometallics
1996, 15, 4832.
Inorganic Chemistry, Vol. 43, No. 6, 2004 2187

Tsai et al.
7.10 (m, 1H, pyrrole CH), 6.12 (m, 2H, pyrrole CH), 3.46 (s, 2H,
CH2), 2.31 (s, 6H, NMe2). 13C NMR (CDCl3): 149.1 (s, CON),
138.7 (s, phenyl Cipos), 128.6 (d, JCH ) 158 Hz, phenyl CH), 126.2
(s, pyrrole Cipso), 123.2 (d, JCH ) 162 Hz, phenyl CH), 122.9 (d,
JCH ) 162 Hz, phenyl CH),119.2 (d, JCH ) 175 Hz, pyrrole CH),
115.4 (d, JCH ) 170 Hz, pyrrole CH), 108.4 (d, JCH ) 173 Hz,
pyrrole CH), 55.3 (t, JCH ) 136 Hz, CH2N), 43.0 (q, JCH ) 135
Hz, NMe2). Anal. Calcd for C14H17N3O: C, 69.11; H, 7.04; N,
17.27. Found: C, 69.25; H, 6.72; N, 17.46.
Experimental Section
General Procedure. All reactions were performed under a dry
nitrogen atmosphere using standard Schlenk techniques or in a
glovebox. Toluene, diethyl ether, and tetrahydrofuran were dried
by refluxing over sodium benzophenone ketyl. CH2Cl2 was dried
over P2O5. All solvents were distilled and stored in solvent
reservoirs which contained 4 Å molecular sieves and were purged
with nitrogen. 1H and 13C NMR spectra were recorded on a Bruker
AC 200 spectrometer. Chemical shifts for 1H and 13C spectra were
recorded in parts per million (ppm) relative to the residual protons
and 13C of CDCl3 (δ 7.24, 77.0) and C6D6 (δ 7.15, 128.0). Elemental
analyses were performed on a Heraeus CHN-OS Rapid Elemental
Analyzer at the Instrument Center, NCHU. [C4H3NH(CH2NMe2)-
2] was prepared according to a previously reported procedure.8
AlMe3 and phenyl isocyanate (Aldrich) were used as received.
[C4H3N(CH2NMe2)-2]AlMe2 (1). A 100 mL Schlenk flask
containing [C4H3NH(CH2NMe2)-2] (2.0 g, 16 mmol) was cooled
to 0 °C and 20 mL of methylene chloride was added. To the
methylene chloride solution AlMe3 (2 M, 8.0 mL, 16 mmol) was
added dropwise through a syringe with stirring. The solution was
stirred at room temperature for 12 h after the addition was
completed. The resulting solution was vacuum-dried to yield 2.50
g of white solid in 88% yield. H NMR(CDCl3): 6.81 (s, 1H,
pyrrole CH), 6.23 (m, 1H, pyrrole CH), 6.06 (m, 1H, pyrrole CH),
3.88 (s, 2H, CH2), 2.56 (s, 6H, NMe2), -0.68 (s, 6H, AlMe2). 13
NMR (CDCl3): 131.6 (s, pyrrole Cipos), 123.2 (d, JCH ) 180 Hz,
pyrrole CH), 109.9 (d, JCH ) 166 Hz, pyrrole CH), 104.3 (d,
JCH ) 167 Hz, pyrrole CH), 59.9 (t, JCH ) 140 Hz, CH2N), 45.7
(q, JCH ) 139 Hz, NMe2), -11.9 (q, JCH ) 114 Hz, AlMe2). Anal.
Calcd for C9H17AlN2: C, 59.98; H, 9.51; N, 15.54. Found: C,
60.03; H, 9.42; N, 15.32.
{C4H3N[CH2NPh(CONMe2)]-2}AlMe2 (2). To a 100 mL
Schlenk flask containing 1 (1.23 g, 6.8 mmol) was added 20 mL
of toluene and the solution was cooled to 0 °C. To the toluene
solution PhNCO (0.81 g, 6.8 mmol) in 20 mL of toluene in another
flask was added dropwise with stirring. The solution was stirred at
room temperature for 24 h after the addition was completed. The
resulting solution was vacuum-dried to yield a brick red solid, which
was recrystallized from methylene chloride to afford 1.12 g of brick
crystals in 55% yield. 1H NMR (CDCl3): 7.35-7.24 (m, 2H, phenyl
CH), 6.93 (m, 3H, phenyl CH), 6.83 (s, 1H, pyrrole CH), 6.00 (m,
1H, C4H3N), 5.72 (m, 1H, pyrrole CH), 4.76 (s, 2H, CH2N), 2.72
(s, 6H, NMe2), -0.64 (s, 6H, AlMe2). 13C NMR (CDCl3): 161.5
(s, NCO), 141.9 (s, phenyl Cipso), 130.9 (s, pyrrole Cipso), 129.9 (d,
JCH ) 166 Hz, phenyl CH), 127.1 (d, JCH ) 163 Hz, phenyl CH),
126.0 (d, JCH ) 171 Hz, phenyl CH), 125.8 (d, JCH ) 157 Hz,
pyrrole CH), 109.2 (d, JCH ) 166 Hz, pyrrole CH), 107.3 (d,
JCH ) 167 Hz, pyrrole CH), 52.1 (t, JCH ) 140 Hz, CH2N), 39.1
(q, JCH ) 140 Hz, NMe2), -9.6 (q, JCH ) 112 Hz,AlMe2). Anal.
Calcd for C16H21N3OAl: C, 64.20; H, 7.41; N, 14.04. Found: C,
63.25; H, 7.30; N, 13.91.
{C4H3N(CH2NMe2)-2-[C(dO)NPh]-1}AlMe2 (4a) and {C4H3N-
(CH2NMe2)-2- [CO(dNPh)]-1}AlMe2 (4b). A 100 mL Schlenk
flask containing 3 (4.20 g, 17.2 mmol) was cooled to 0 °C and 20
mL of methylene chloride was added. To the methylene chloride
solution AlMe3 (2 M, 8.6 mL, 17.2 mmol) was added dropwise
through a syringe with stirring. The solution was stirred at room
temperature for 12 h after the addition was completed. The resulting
solution was vacuum-dried and crystallized again from methylene
chloride to yield 4.0 g of white solid in 78% yield. 1H NMR
(CDCl3): 7.62, 7.38-7.07, 6.19, 3.86, 3.79, 2.47, 2.43, -0.98,
-1.29. 13C NMR (CDCl3): 156.7, 147.2, 144.2, 129.2, 128.8, 128.4,
127.5, 123.9, 123.5, 122.7, 122.5, 121.8, 116.7, 115.6, 109.1, 108.9,
57.8, 57.2, 46.2, 45.7, -11.9. Anal. Calcd for C16H22AlN3O: C,
64.20; H, 7.41; N, 14.04. Found: C, 64.03; H, 7.16; N, 13.91.
AlMe3{C4H3N(CH2NMe2)-2-[C(dO)NPh]-1}AlMe2 (5). A 100
mL Schlenk flask containing 3 (2.60 g, 10.7 mmol) was cooled to
0 °C and 20 mL of methylene chloride was added. To the methylene
chloride solution AlMe3 (2 M, 10.7 mL, 21.4 mmol) was added
dropwise through a syringe with stirring. The solution was stirred
at room temperature for 12 h after the addition was completed.
The resulting solution was vacuum-dried and crystallized again from
methylene chloride to yield 2.76 g of white solid in 70% yield. 1H
NMR (CDCl3): 7.39-7.27 (m, 4H, phenyl and pyrrole CH), 7.05-
7.01 (m, 2H, phenyl CH), 6.39 (m,1H, pyrrole CH), 6.28 (m, 1H,
pyrrole CH), 3.92 (s, 2H, CH2N), 2.56 (s, 6H, NMe2), -1.23 and
-1.27 (AlMe2 and AlMe3, 15H). 13C NMR (CDCl3): 158.9 (s,
CON), 141.5 (s, phenyl Cipso), 129.3 (d, JCH ) 162 Hz, phenyl
CH), 126.8 (d, JCH ) 162 Hz, phenyl CH), 126.3 (d, JCH ) 160
Hz, phenyl CH), 124.8 (d, JCH ) 194 Hz, pyrrole CH), 122.5 (s,
pyrrole Cipso), 118.1 (d, JCH ) 174 Hz, pyrrole CH), 111.1 (d,
JCH ) 176 Hz, pyrrole CH), 57.0 (t, JCH ) 141 Hz, CH2N), 46.1
(q, JCH ) 141 Hz, NMe2), -8.3 (q, JCH ) 111 Hz, AlMe), -11.9
(q, JCH ) 108 Hz, AlMe). DEPT-135 13C NMR spectra were used
for identifying the Cipso and CH of phenyl and pyrrole groups. Anal.
Calcd for C19H31Al2N3O: C, 61.44; H, 8.41; N, 11.31. Found: C,
61.02; H, 8.61; N, 10.79.
1
C
Acknowledgment. We thank the National Science Coun-
cil of Taiwan for financial support and the National Center
for High Performance Computing for databank searches. We
thank Professor Hon Man Lee for proofreading the manu-
script and also thank Gene-Hsiang Lee of National Taiwan
University for solving the molecular structure of compound
1.
{C4H3N(CH2NMe2)-2-[C(dO)NHPh]-1} (3). A 100 mL Er-
lenmeyer flask was charged with [C4H3NH(CH2NMe2)-2] (4.0 g,
32.2 mmol) and 20 mL of diethyl ether. To the stirred solution,
excess phenyl isocyanate (4.5 g, 37.8 mmol) was added dropwise
and the combined solution was stirred for 1 h. The solution was
vacuum-dried and the resulting solid was washed with heptane to
Supporting Information Available: Theoretical calculation
results and X-ray crystallographic files in CIF format for compounds
1, 2, 3, 4b, 5, and DMPU. This material is available free of charge
via the Internet at http://pubs.acs.org.
1
remove excess phenyl isocyanate. Yield: 88% (6.91 g). H NMR
(CDCl3): 12.91 (s, br, 1H, PhNH), 7.60-7.32 (m, 5H, phenyl CH),
IC035261Z
2188 Inorganic Chemistry, Vol. 43, No. 6, 2004